TREM2 and cancer: TREM2 is generally considered to be an anti-tumor factor, acting through the Sky and Wnt1/β-catenin pathways in multiple cancers, including hepatocellular carcinoma (11), colorectal cancer (12), and lung cancer (13); however, TREM2 is expressed at higher levels in gastric cancer (14), and its up-regulation is related to poor patient prognosis.